It is required for a display apparatus to comprise a gate driving circuit so as to realize a normal display. Specifically, the gate driving circuit comprises multiple stages of shift registers in a cascade connection.
Particularly, a structure of a shift register is illustrated in FIG. 1. The shift register comprises an input module, an output module and an output control module. The input module comprises a transistor M1, the output module comprises transistors M2 and M3, and the output control module comprises transistors M4, M5, C1 and a capacitor C2, wherein M1-M5 are all PMOSFETs which are turned on by a low level. The timing sequence of the shift register in an operational process is illustrated in FIG. 2. At period t1, a start signal input from a start signal input terminal STV and a first clock signal input from a first clock signal input terminal CK1 are low level signals, and a second clock signal input from a second clock signal input terminal CK2 is a high level signal. At this time, transistors M1, M2, M3, M4 and M5 are all turned on, and the signal output terminal Output outputs a high level (an inactive signal). At period t2, the start signal input from the start signal input terminal STV and the first clock signal input from the first clock signal input terminal CK1 are high level signals, and the second clock signal input from the second clock signal input terminal CK2 is a low level signal, such that transistors M1, M4 and M5 are turned off. Transistors M2 and M3 are turned on due to the effect of C2 and C1, and the signal output terminal Output outputs a low level (an active signal).
The inventor(s) found that, when the second clock signal input from the second clock signal input terminal CK2 varies, the signal on the gate of transistor M2 would be affected by the coupling capacitance formed between the gate and the drain of transistor M2, so that the output signal output by the output terminal Output is affected, thus deteriorating the output signal and affecting the output effect of the shift register.